The present invention relates to method and apparatus for splicing optical fibres. More in particular, the present invention relates to a method of splicing optical fibres in which the ends of the fibres are cut at a non-perpendicular angle.
Optical fibres can be interconnected or “spliced” in several ways. Fusion splicing involves heating the ends of the fibres to be spliced in order to produce a continuous transition. Mechanical splicing involves abutting the fibre ends in a suitable support or “splice”. As mechanical splicing does not require any heating, it is often preferred for splicing in the field. The mechanical splice device needs to be carefully designed to achieve a proper alignment of the fibre ends. Examples of such splice devices are disclosed in U.S. Pat. Nos. 4,687,288 and 5,394,496. A special type of releasable mechanical fibre splice is a fibre optic connector. An example of such a connector is disclosed in U.S. Pat. No. 4,705,352.
It is well known to cut optical fibres at a predetermined angle to produce a suitable fibre end face for splicing and/or connecting. U.S. Pat. No. 4,229,876, for example, discloses an optical fibre cleaver or “breaker” which can be used for this purpose.
Traditionally fibres have been cleaved under a right angle, resulting in a fibre end face which is perpendicular to the longitudinal axis of the fibre. It has been found, however, that reflection losses can be significantly reduced by cleaving the fibres at a non-perpendicular angle, that is, at an angle which deviates from the perpendicular. International Patent Application WO 98/54608, for example, discloses a tool for angled cleaving of optical fibres. The fibres are cleaved with ends which are consistently angled at between 1° and 20°, preferably 5° to 10°, away from the perpendicular to the fibre axis.
Although fibres having such an angled end face potentially perform very well, a problem arises when they are to be spliced. For the angled end faces to abut properly, leaving virtually no gap, the end faces have to be parallel. This requires the fibres to have a very specific keyed orientation when they are accommodated in a splice body. In existing splicing methods, the relative orientation of the fibres is arbitrary. Of course it is possible to experimentally determine the proper orientation of the fibres by accommodating them in a splice and then measuring the reflection losses at various orientations. This is, however, both expensive and time consuming and may cause the fibre end faces to be damaged. Alternatively optical gel (index matching gel) may be used to reduce the adverse effects of an improper relative orientation of the fibre end faces but it has been found that the advantageous effects of the angled cleaving may still be lost.